If you were looking for something to believe in this last decade, you couldn't have done much better than that zone of music some of us have taken to calling the hardcore continuum.

In the noughties, sound-wise that meant grime and dubstep primarily (plus offshoots and edge cases like bassline and funky). But scene-wise it's fundamentally the same London-centric (but not limited to London) subculture that coalesced in the early 1990s and is based around pirate radio, dubplates, rewinds, MCs etc. What made it something to believe in? Well, there was the power of the music, obviously, and the way it seemed propelled by some relentless forward drive that was less a matter of ideology or aesthetic stance on the part of its creators than an inherent force within the music itself. Then there was its Britishness, and the things it told you about modern Britain: not always pretty, and not always communicated through words but through beats, bass, space and atmosphere. And finally it's because the music stirred up and surrounded itself with sharp thought at every level, from producers and artists to fans and professional observers. Some of this chatter was your typical inwardly focused "what's hot, what's not" discussion that you get in any musical niche, but quite a lot of it was attempting to work out the buried credo within the music, the reasons why it mattered and was so belief-worthy.

The hardcore continuum's claim to pre-eminence has always been that it's not just dance music. That's no slight to dance music, but the truth is that there's tons of it in the world, all different flavours, and if you fancied shaking your stuff in the noughties then you'd probably have been better off with hip-hop, or dancehall, or that hardy perennial house music. With jungle/garage/grime/dubstep, there's always been something extra, an X factor that made it "dance music + _____". The two main things that filled the blank were a) innovation, the idea that no other music around moved faster or mutated wider, and b) a relationship to "the real", whether that was coded as "street knowledge", "the dark side", late capitalism/post-socialist Britain, etc. In the noughties, the danceability element even slipped somewhat: grime was more moshable than groovy, while dubstep could be a bit slow-skank sluggish and head-noddy. But more relevant to this survey is that the pulse of those X-tra factors seemed to grow fainter as the decade proceeded, or at least more indistinct and muddled.

Let's look at innovation first. Dubstep's big foundational club called itself FWD>> but I think what happened in the noughties was that the innovatory drive shifted its axis and became less extensive than intensive: instead of giant strides into the unknown, it was about a quest for under-explored spaces and new hybrid possibilities within the frontiers staked out during the 90s. That decade had been convulsed by an acceleration (in tempo and complexity of rhythm) that impacted the dancefloor massive like g-force. Change was experientially measurable all through the 90s, in the way that the beats kept on testing the bodies of ravers. That headlong surge lasted from 1990-97: bpm kept rising, breakbeat science and bass-warpage got ever more intricate yet devastating. And then it hit a dead end. So the music stepped sideways into house-inspired sensuality, with speed garage. Assimilating R&B, the music got slower, slinkier and sexier and turned into 2step (and it's worth remembering that this decade started with 2step garage still reigning over the pop charts). Then UK garage itself split in two like a fertilised egg forming twins. Except these were non-identical twins: grime and dubstep, so unlike yet indissolubly bonded.

Where grime was verbose and articulate, dubstep was mute and atmospheric; where grime was aggressive and manic, dubstep was meditational and subdued. Although UK garage was the immediate ancestor, in crucial ways they were both more like the reactivation of different aspects of jungle. Grime's rapid-spat chat was the blossoming of the latent potential in jungle for the MC to become a star to rival the DJ, a genuine creative force. Dubstep picked up on the bass-drop, the aura of dread, the rootical echoes of 1970s reggae at its peak of spiritual militancy. But it shed jungle's hyperkinetic tempo and at the extreme (the style known as half-step) became as torpid as trip-hop. (Small wonder that Bristol was dubstep's second city.)

Grime and dubstep were brothers, often cohabiting on the same pirate stations, like Rinse FM. You didn't have to choose between the two, of course, but on a visceral, almost involuntary level the choice made itself for me. Grime was the one I believed in, or rather the one that kept me believing. From 2002-05 it felt like an unstoppable force, but in retrospect I can see why it never quite managed to bust through into the mainstream, at least on its own terms (as pure uncut grime as opposed to the innocuous poppified version that's topped the charts these last couple of years). With grime, those two X-tra factors were operating at full-tilt. The innovation was in your face, the jagged beats and harsh electronics making it music that few people would put on at home as relaxing listening. And then the real-ness was off the charts. For most British fans, I suspect, it was simply too close to home. Unlike American gangsta rap, which was well-produced and cinematic and had an element of exotic remoteness, grime was always going to remind non-converts, people from outside the scene itself, of hooded youths on the top deck of buses sodcasting tinny music at top volume out of their mobiles. But when it tried to nice itself up and play the pop game, it fell between two stools, as with Kano and Lady Sov's crossover bids.

In contrast, dubstep's slightly lower levels of the two X-tra factors enabled it to prosper. Not in chart terms obviously, but it steadily accumulated an international audience (who could understand its non-verbal message in a way they could never with grime's spraying verbals). It also became an album-based form that captivated listeners who rarely or never actually checked out dubstep as a dancefloor scene. Burial was the great genre ambassador here, but figures like Shackleton, Pinch, Martyn and 2562 also helped to spread the music's reach by making it home-listening compatible. For much of the noughties, my annual favorites list has included a bunch of dubstep full-lengths but as an ex-raver used to the artificial NRG vibe I've generally found the music too downtempo as a dancefloor experience. With a handful of exceptions (Skream's Midnight Request Line, Benga & Coki's Nite), the Big Tracks rarely feel like anthems to my ears, although the scene's bangers can be impressively ugly and inhuman (as with Coki's Spongebob, whose metallic wobble-riff is apparently made from the cartoon character's laugh slowed down drastically).

My other misgiving about dubstep was always the discernible disconnect between what the music was attempting to signify – tension, menace, sufferation, Babylon-shall-fall – and the affable mellowness of the scene itself. If you went to a jungle or UK garage night back in the day, there'd be a palpable tension in the audience that could be uncomfortable but lent the experience a certain electricity. But with dubstep, there was a degree of non-congruence between the music and the vibe. Being extensions of rave, jungle and garage were weekender scenes; their audiences had stuff they needed to release. I don't get the sense that the same function of social catharsis was ever really served by dubstep. In the early days the scene's foundational club FWD>> was a Sunday night event, which suggests that the people attending had more flexible lives than hardcore ravers. It's a different demographic, with a much higher proportion of people who've been through (or are still in) higher education, and who work in jobs to do with information, media, design, etc. Everybody finally waking up to this mismatch between the scene's signifiers and its actual social reality might explain why dubstep has veered so dramatically in the last year or so from dread and darkness towards a cartoon ultra-brightness suggestive both of videogames and psychedelics. This year's array of post-dubstep sounds are no longer chained to realness but are much more about garish hyper-reality. "Purple", the buzz-term for the Bristol-based micro-genre created by Joker, Guido and others, is colour rich in psychotropic associations, from Jimi's Purple Haze to the "purple drank" cough syrup that Dirty South gangsta rappers love to sip.

And then there's funky: another London pirate continuum offshoot that's unshackled itself from the real. Merging the traditions of disco house and Caribbean upfulness (soca, etc), funky is about pure celebration, with a songbook that entirely consists of songs of love'n'desire or injunctions to party. Funky gets near to being just dance music without any X-factor element. Certainly the realness that grime and dubstep both overstated in their different ways now mainly subsists in funky's demographic, the fact that its audience is street, from "the ends". As for the other X factor, funky's champions point to the broken rhythms and lo-tech grittiness of some productions as proof that the spirit of innovation does persist here, it just doesn't make such a big song'n'dance about da phuture like yer Photeks and Goldies did back in the day.

One way of thinking about the hardcore continuum is as a game of two halves: the 90s and the noughties. The question now is whether the current moment is just extra time or whether there can actually be a third half. Or is UK urban underground dance turning into a completely different game, a whole other sport with new rules?